'Brain hole' finding gives new insight

By Peter MunroApril 16 2002

Sydney scientists have discovered a "black hole" in the brain that may cause the symptoms of Parkinson's disease.

The scientists, from the Prince of Wales Medical Research Institute, found that an important group of nerve cells, previously thought to be merely inactive in people with Parkinson's disease, are in fact entirely missing.

The disease affects more than 50,000 Australians.

The missing cells, or neurons, are in the brain cortex at the crown of the skull, and are responsible for fine-motor actions such as writing, doing up buttons or playing a musical instrument.

Glenda Halliday, senior researcher at the Medical Research Institute, said the discovery that the cells are missing may reveal the cause of Parkinson's disease.");document.write("

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"The whole concept of how Parkinson's worked was that these neurons were there but didn't work. We have found that they are not there at all," she said. "It means we will have a better chance of finding the cause of the disease."

Associate Professor Halliday and her co-researcher found the nerve cells started to die at the onset of the symptoms of Parkinson's disease, and that up to 80 per cent had disappeared within 10 years of diagnosis.

The gap in the brain left by the death of the cells could only be seen after comparing brain tissue from people who died from Parkinson's to control brain tissue, held as part of a Sydney-wide brain donor program for medical research on Parkinson's and dementia.

The breakthrough turns on its head scientific theory about the possible causes of the symptoms of the disease.

It had been thought that low levels of the chemical dopamine, as a result of the death of cells at the base of the brain which stimulate basic movements such as walking and talking, caused the cortex nerve cells to be inactive.

It was not known that the cortex nerve cells had died out.

Current drug treatments do not take into account that these brain cells are dying. One such drug, levodopa, which does reduce tremors for about the first five years of medication, focuses instead on boosting dopamine levels, in the expectation that this will reactivate the cortex.

The discovery could lead to the development of new treatments for Parkinson's. One approach might involve activating other parts of the cortex to compensate for the missing cells, Professor Halliday said.

Victor Fung, a neurologist at Westmead Hospital, said the discovery may explain why certain parts of the brain do not respond to treatment, and why other parts lose responsiveness to treatment after a few years.

"It can help us to begin to make sense of Parkinson's disease and help us plan future treatment," Dr Fung said.